JP2023124060A - Shift control device for automatic transmission - Google Patents

Abstract

To provide an automatic-transmission shift control apparatus capable of preventing a busy shift from occurring during an automatic travel where a vehicle travels with drive power and brake power automatically controlled.SOLUTION: Controls include: determining on practice of automatic travel where a vehicle is traveling by establishing a requirement value of power of an engine without a driver operating on an accelerator (step S1); determining that a vehicular speed is equal to a first speed or higher at which an upshift from a first shift ratio to a second shift ration occurs in a case where an output of power from the engine is required, and that the speed is equal to or lower than a second speed at which a downshift from the second shift ratio to the first shift ratio occurs in a case where an output of power from the engine is not required (step S4), and performing an automatic travel; and inhibiting a shift from the first shift ratio or the second shift ratio in a case where the vehicular speed is equal to or higher than the first speed, and equal to or lower than the second speed (step S6).SELECTED DRAWING: Figure 3

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for an automatic transmission configured to be capable of setting a plurality of shift stages, and particularly to an automatic transmission while the driver is driving without operating the accelerator or brake. It relates to a gear shift control device.

Patent Document 1 discloses an automatic control system that uses a set vehicle speed and a set vehicle-to-vehicle distance as target values and controls driving force and braking force without the driver operating the accelerator or braking while executing cruise control. A shift control device for a transmission is described. In order to suppress the occurrence of a busy shift in which the automatic transmission shifts frequently during cruise control, the shift control device is designed to increase the vehicle speed at a higher speed than the upshift line defined by the normal shift map during driving. Shifts are performed with reference to an upshift map with a wide range of parameters, and during braking, the shift is performed with reference to a downshift map that defines a downshift line on the higher vehicle speed side than the downshift line defined in the normal shift map. is configured to Also, during coasting, the vehicle is configured to shift gears with reference to a normal shift map.

Japanese Patent Application Laid-Open No. 2003-329123

According to the shift control device described in Patent Literature 1, during cruise control, the map to be referred to is switched according to the running state of driving running, decelerating running, and coasting. Therefore, when the vehicle speed changes due to the driving environment such as the slope angle of the road surface, the driving force and braking force required for the vehicle change and the map to be referred to is switched. In such a case, since the shift stage to be set differs depending on the map to be referred to, a busy shift occurs in which upshifts and downshifts are frequently performed, and the driver may feel uncomfortable with the shock associated with the shift. be.

The present invention has been made with a focus on the above technical problems, and is gear shift control for an automatic transmission capable of suppressing the occurrence of a busy shift during automatic travel in which driving force and braking force are automatically controlled. The object is to provide an apparatus.

In order to achieve the above objects, the present invention provides an input shaft connected to an engine, an output shaft connected to drive wheels, and a transmission gear ratio between the input shaft and the output shaft that is set to a plurality of predetermined values. and a controller that sets the gear ratio of the transmission mechanism based on the power demand of the engine and the vehicle speed. In the gear shift control device for a machine, the controller includes a driving mode determination unit that determines automatic driving by determining a required amount of power of the engine without a driver's accelerator operation, and a driving mode determination unit that determines that the vehicle is traveling automatically. When it is requested to output power from the engine at a first vehicle speed or higher at which the first gear ratio is switched to a second gear ratio that is smaller than the first gear ratio, and the power is output from the engine A vehicle speed determination unit that determines that the vehicle is traveling at a vehicle speed equal to or lower than a second vehicle speed at which the vehicle is switched from the second gear ratio to the first gear ratio when the request is not made, and the travel mode determination unit determines that the vehicle is automatically traveling. and the vehicle speed determination unit determines that the vehicle speed is equal to or higher than the first vehicle speed and equal to or lower than the second vehicle speed, the gear ratio is changed from the first gear ratio or the second gear ratio. and a shift prohibition section for prohibiting the shift of the gear.

Further, in the present invention, the shift prohibiting section may prohibit shifting from the second gear ratio.

Further, in the present invention, the controller controls the vehicle speed determination unit to determine whether the actual vehicle speed is equal to or higher than the first vehicle speed during steady-state driving in which the difference between the target vehicle speed for automatic driving and the actual vehicle speed is less than a predetermined difference. In addition, it may be determined that the vehicle speed is equal to or lower than the second vehicle speed.

Further, in the present invention, the steady running may include running in which the difference between the target vehicle speed and the actual vehicle speed is less than a predetermined difference for a predetermined period of time or longer.

Further, in the present invention, the target vehicle speed may include a vehicle speed preset for the automatic travel.

Further, the present invention further includes a vehicle-to-vehicle distance measuring device that measures a vehicle-to-vehicle distance to a preceding vehicle, wherein the automatic driving includes follow-up driving in which the vehicle travels while maintaining the vehicle-to-vehicle distance at a predetermined distance. The target vehicle speed may include a vehicle speed for maintaining the inter-vehicle distance at the predetermined distance.

Further, in the present invention, the controller may permit shifting from the first gear ratio or the second gear ratio when a predetermined cancellation condition is satisfied.

Further, in the present invention, the predetermined cancellation condition may include a condition that the driver performs a driving operation or a braking operation.

Further, in the present invention, the predetermined cancellation condition may include a condition that there is a deceleration request by another control.

The present invention further comprises a sensor for detecting the slope angle and the slope direction of the road surface ahead, and the predetermined cancellation condition is that the slope direction of the road surface ahead is the descending direction and the slope angle of the road surface may include a condition that is greater than or equal to a predetermined angle.

According to the present invention, it is determined that the vehicle is automatically traveling by determining the required amount of power of the engine without the driver operating the accelerator. Further, when the vehicle speed is equal to or higher than the first vehicle speed at which the first gear ratio is upshifted from the first gear ratio to the second gear ratio when there is a request to output power from the engine, and when there is no request to output power from the engine. , determines that the vehicle speed is equal to or lower than the second vehicle speed for downshifting from the second gear ratio to the first gear ratio. That is, it is determined whether or not the vehicle speed during automatic driving is a vehicle speed at which a busy shift occurs. Then, when it is determined that the vehicle speed is a busy shift, shifting from the first gear ratio or the second gear ratio is prohibited. Therefore, even if the required driving force changes slightly due to factors such as changes in the road surface gradient and changes in the distance to the vehicle ahead, the shift is repeated between the first gear ratio and the second gear ratio. It is possible to suppress the occurrence of hunting caused by

1 is a schematic diagram for explaining an example of a configuration of a vehicle equipped with an automatic transmission and a controller that controls an engine and an automatic transmission according to an embodiment of the invention; FIG. It is a figure which shows an example of a shift map. 4 is a flowchart for explaining an example of control executed by the shift control device according to the embodiment of the invention; 7 is a flowchart for explaining a control example for determining whether a cancellation condition is satisfied;

An example of a vehicle equipped with an automatic transmission according to an embodiment of the invention is shown in FIG. A vehicle Ve shown in FIG. 1 is a vehicle Ve having an engine (ENG) 1 as a driving force source. 3 is connected to the input shaft 2 of the automatic transmission 3, and a pair of rear wheels (hereinafter referred to as drive wheels) 8 are connected to the output shaft 4 of the automatic transmission 3 via a propeller shaft 5, a differential gear unit 6, and a drive shaft 7. ing.

The engine 1 is a conventionally known gasoline engine, diesel engine, or the like, and controls the opening of a throttle valve (not shown) (hereinafter referred to as throttle opening) according to the driving force required for the vehicle Ve. The driving torque is output by combusting a mixture of air supplied through the throttle valve and fuel ejected from the combustion injector. In addition, the engine 1 stops the combustion of the air-fuel mixture, that is, stops the supply of fuel, closes the throttle valve, etc., so that the braking torque (engine brake ) can be output.

The automatic transmission 3 can be configured in the same manner as a conventionally known stepped automatic transmission, and includes engagement mechanisms such as a plurality of clutch mechanisms and brake mechanisms. is configured to set a predetermined gear stage (gear ratio) by engaging the engagement mechanism. That is, by releasing a predetermined engagement mechanism and engaging another engagement mechanism, or by releasing at least one engagement mechanism among a plurality of engagement mechanisms, the engagement mechanism that has been released By engaging at least one of the engaging mechanisms, the gear stage can be switched. The engagement mechanism that engages and disengages to set the gear stage may be a friction type engagement mechanism or a meshing type engagement mechanism. Further, the engagement mechanism may be a hydraulic engagement mechanism that engages and releases by hydraulic pressure, or an electromagnetic engagement mechanism that engages and releases by electromagnetic force. .

In addition to normal running in which the requested amount of power output from the engine 1 is determined according to the driver's accelerator operation, the vehicle Ve requests the power output from the engine 1 without the driver's accelerator operation. It is configured to enable cruise travel in which the amount of travel is determined. Further, this cruise running is configured to be able to perform follow-up running in which the driving force and the braking force are automatically controlled so as to maintain the inter-vehicle distance from the preceding vehicle.

In this cruising, the driving force and the braking force are determined using the vehicle speed appropriately set by the driver and the inter-vehicle distance according to the set vehicle speed as target values, and the engine 1 outputs based on the driving force and the braking force. It is configured to define a power demand. Therefore, as a device for cruising, a cruise switch 9 that is operated when the driver requests cruising, a distance between the vehicle such as a radar or a laser for measuring the distance between the vehicle and the vehicle in front, or an in-vehicle camera. A meter 10 is provided. In addition to controlling the driving force and braking force according to the target vehicle speed and the target inter-vehicle distance by turning on the cruise switch 9, for example, when the preceding vehicle stops, the own vehicle is also stopped, and then , the driving force and the braking force for stopping and starting the vehicle, such as starting the own vehicle when the preceding vehicle starts moving, are configured. In other words, the vehicle is configured so that it can automatically travel by controlling the driving force and the braking force corresponding to all vehicle speeds from low vehicle speeds including stop to high vehicle speeds. In the following description, control of driving force and braking force for cruising is referred to as cruise control.

A vehicle Ve shown in FIG. 1 includes an electronic control unit (hereinafter referred to as ECU) 11 for controlling the engine 1 and the automatic transmission 3 during normal running and cruising. The ECU 11 corresponds to the "controller" in the embodiment of the present invention, and is composed mainly of a microcomputer as in the conventional ECU, and it controls input signals, pre-stored maps and arithmetic expressions. It is configured to determine the torque to be output from the engine 1, the gear stage to be set by the automatic transmission 3, and the like, based on the above.

The ECU 11 shown in FIG. 1 includes an engine control section 12 for controlling the engine 1 and a shift control section 13 for controlling the automatic transmission 3 . The ECU 11 also includes an accelerator opening sensor 14 for detecting the operation amount of an accelerator pedal (not shown), an engine speed sensor 15 for detecting the engine speed, and an automatic transmission 3 such as a propeller shaft 5. An output shaft rotation speed sensor 16 for detecting the rotation speed of a rotating member on the output side, a cruise switch 9, an inter-vehicle distance measuring device 10, etc. are connected, and the detection values of these sensors 9, 10, 14, 15, 16 are configured to be entered.

The engine control unit 12, for example, based on the accelerator opening input from the accelerator opening sensor 14, the rotation speed corresponding to the vehicle speed input from the output shaft rotation speed sensor 16, and a map stored in advance. A driving force required for the vehicle Ve is obtained. Further, when the cruise switch 9 is turned on, the set vehicle speed or the vehicle speed required to shorten the inter-vehicle distance to the preceding vehicle using the set vehicle speed as the upper limit vehicle speed is set as the target vehicle speed, and the target vehicle speed and the actual vehicle speed are set. The driving force required for the vehicle Ve is obtained based on the difference between the .

Next, the throttle opening is determined based on the required driving force obtained as described above, and the signal is output to the actuator for controlling the throttle opening. In addition to the throttle opening, the fuel injection amount is also determined, and a signal thereof is output to the fuel injection device. That is, the engine control section 12 outputs signals to various devices that control the output torque of the engine 1 . In FIG. 1, for the sake of convenience, these output signals are collectively referred to as "torque output instruction".

The shift control unit 13 is configured to set a shift stage based on a shift map using the throttle opening and the vehicle speed as parameters, as in a conventional automatic transmission control device. A part of the shift map is shown in FIG. In FIG. 2, the horizontal axis represents the vehicle speed and the vertical axis represents the throttle opening. The solid line indicates the upshift line, the dashed line indicates the downshift line, and "○" indicates the coast down point (CD point). is shown.

The upshift line shown in FIG. 2 is for determining whether to upshift from the first forward speed to the second forward speed. It is determined to upshift when the vehicle speed increases across the upshift line. The downshift line shown in FIG. 2 is for determining whether to downshift from the second forward speed to the first forward speed. It is determined to shift. Note that the gear ratio of the first forward speed corresponds to the "first gear ratio" in the embodiment of this invention, and the gear ratio of the second forward speed corresponds to the "second gear ratio" of the embodiment of the invention. corresponds to

Further, as for the coast-down point shown in FIG. 2, when the vehicle speed is on the lower vehicle speed side than the coast-down point during coasting with the throttle opening 0 (zero), the first forward speed is selected, and is lower than the coast-down point. In the case of the high vehicle speed side, the second forward speed is selected.

Therefore, when the vehicle is traveling at a vehicle speed between the first vehicle speed V1, which is the vehicle speed on the lowest vehicle speed side of the upshift line, and the second vehicle speed V2, which corresponds to the coast down point, more specifically, In the hatched operating region shown in FIG. 2 where the throttle opening is less than the predetermined opening, the second forward speed is set when the throttle valve is open, and the second forward speed is set when the throttle valve is closed. 1st gear is set.

That is, when the vehicle is traveling at a vehicle speed between the first vehicle speed V1 and the second vehicle speed V2, the opening and closing operations of the throttle valve are repeatedly performed, and accordingly, upshifts and downshifts are repeatedly performed. In other words, the driving region of the first vehicle speed V1 or higher and the second vehicle speed or lower is a busy shift region in which the shift frequency is relatively high. Note that the upshift from the first forward speed to the second forward speed in the busy shift region is started after a predetermined time has elapsed after the throttle valve is opened.

On the other hand, during normal driving, the throttle valve opens and closes according to the driver's operation of the accelerator, and accordingly, upshifts and downshifts are performed. Therefore, even if upshifts and downshifts are repeatedly performed in the busy shift region, and shift shocks are repeatedly generated, the shift shocks are likely to be tolerated by the driver. Therefore, during normal running, the gear is set based on the shift map.

In contrast, during cruising, the throttle valve opens and closes without the driver operating the accelerator. Therefore, if upshifts and downshifts are repeatedly performed and shift shocks are repeatedly generated, the driver may feel uncomfortable.

Therefore, the shift control device in the embodiment of the present invention is configured to prohibit downshifting from the second forward speed to the first forward speed in the busy shift region during cruising.

That is, the shift control unit 13 determines the required power amount of the engine 1 according to the driver's accelerator operation, and determines the required power amount of the engine 1 without the driver's accelerator operation. A driving mode determination unit 17 for determining in which driving mode the vehicle is traveling, cruising or cruising, and a vehicle speed for determining whether the vehicle speed is equal to or higher than the first vehicle speed V1 and equal to or lower than the second vehicle speed V2. The determination unit 18 and the driving mode determination unit 17 determine that the vehicle is cruising, and the vehicle speed determination unit 18 determines that the vehicle speed is equal to or higher than the first vehicle speed V1 and equal to or lower than the second vehicle speed V2. and a shift prohibiting portion 19 that prohibits shifting from the second forward speed when the forward speed is set.

FIG. 3 shows a flow chart for explaining an example of the control executed by the ECU 11 described above. In the control example shown in FIG. 3, first, it is determined whether cruise control is being executed (step S1). This step S1 can be determined based on whether the cruise switch 9 is turned on.

If a negative determination is made in step S1 because the cruise control is not executed, the driving force and braking force are controlled according to the driver's accelerator operation and braking operation, and the driving force and braking force are controlled. It is preferable to set a gear stage, that is, to perform a gear shift. Therefore, if the determination in step S1 is negative, the routine is terminated without prohibiting the shift (step S2). That is, the gear stage is set based on the gear shift map shown in FIG. 2 using the throttle opening and the vehicle speed as parameters, and the gear stage is permitted to be changed. It should be noted that if the shift prohibition control has been executed by the previously executed routine, the shift prohibition control is canceled and the shift is permitted.

Conversely, if the determination in step S1 is affirmative because the cruise control is being executed, it is determined whether or not the vehicle is in a steady running state (step S3). Specifically, whether or not the difference between the target vehicle speed and the actual vehicle speed is equal to or less than a predetermined difference, and whether or not the duration for which the difference between the target vehicle speed and the actual vehicle speed is equal to or less than the predetermined difference is equal to or greater than a predetermined time. to judge whether The target vehicle speed in step S3 may be the vehicle speed set by the driver using the cruise switch 9, or may be the vehicle speed that maintains the distance to the preceding vehicle. Also, the predetermined difference is a predetermined difference such as a driver-tolerable difference between the set vehicle speed and the actual vehicle speed. Furthermore, the predetermined time is a predetermined time for eliminating a situation in which the difference between the target vehicle speed and the actual vehicle speed temporarily becomes equal to or less than the predetermined difference. In step S3, when the vehicle is accelerating or decelerating, that is, when the driving force or braking force is controlled so that the vehicle accelerates or decelerates at a predetermined acceleration or more, it is determined that the vehicle is not in a steady running state. You may

If a negative determination is made in step S3 because the vehicle is not in a steady running state, it is preferable to perform a downshift in order to satisfy the driving force or braking force, or to suppress deterioration of fuel consumption during drive running. It may be preferable to perform an upshift at Therefore, if the determination in step S3 is negative, the process proceeds to step S2. In other words, gear shifting is not prohibited. It should be noted that if the shift prohibition control has been executed by the previously executed routine, the shift prohibition control is canceled and the shift is permitted.

Conversely, if the determination in step S3 is affirmative because the vehicle is in a steady running state, it is determined whether or not the vehicle is in the busy shift region and the high vehicle speed stage is set (step S4). That is, it is determined whether or not the vehicle speed is greater than or equal to the first vehicle speed V1 and less than or equal to the second vehicle speed V2 and the second forward speed is set. Note that the vehicle speed can be obtained based on the detection value of the output shaft rotation speed sensor 16 .

If it is not in the busy shift region, it is preferable to shift gears in order to improve fuel efficiency and drive performance, since shifting between the first forward speed and the second forward speed does not occur frequently. Further, when the first forward speed, which is a low vehicle speed, is set, the engine speed becomes higher than when the second forward speed is set, resulting in worse fuel consumption. In addition, since the amount of change in the driving force relative to the amount of change in the output torque of the engine 1 is large, the controllability may deteriorate. Therefore, when the first forward speed is set, it is preferable to upshift to the second forward speed, which is a high vehicle speed.

Therefore, if the determination in step S4 is negative because the shift is not in the busy shift range or the high vehicle speed stage side is not set, the process proceeds to step S2. In other words, gear shifting is not prohibited. It should be noted that if the shift prohibition control has been executed by the previously executed routine, the shift prohibition control is canceled and the shift is permitted.

Conversely, if the determination in step S4 is affirmative because it is in the busy shift area and the high vehicle speed stage is set, then various conditions are established that make it undesirable to prohibit gear shifting. No, that is, it is determined whether or not a condition for canceling the shift prohibition control is satisfied (step S5). This cancellation condition will be described later.

If the answer to step S5 is affirmative because the cancellation condition is satisfied, the process proceeds to step S2. In other words, the shift from the second forward speed is permitted. Conversely, if the answer to step S5 is negative because the cancellation condition is not satisfied, the shift is prohibited (step S6), and this routine is terminated. That is, even if the throttle valve is closed after the throttle valve is open and the vehicle is running in the busy shift range, the shift prohibition control is executed to maintain the second forward speed.

FIG. 4 shows a flow chart for explaining an example of control for determining whether or not the cancellation condition is met. The control example shown in FIG. 4 can be executed in parallel with the control example shown in FIG. In the control example shown in FIG. 4, first, it is determined whether or not the driver intends to drive the vehicle (step S11). Whether or not the driver intends to perform a driving operation is determined, for example, by whether or not the driver has operated the accelerator (driving operation) to accelerate the vehicle Ve, that is, whether or not the accelerator opening is equal to or greater than a predetermined opening. determine whether or not Alternatively, whether or not the driver has performed a brake operation (braking operation) to decelerate the vehicle Ve, that is, whether or not the brake operation amount is equal to or greater than a predetermined amount, or whether or not the brake pedaling force is equal to or greater than a predetermined pedaling force. to judge. Alternatively, it is determined whether the cruise switch 9 has been turned off.

If the result of step S11 is affirmative because the driver intends to drive the vehicle, a flag indicating that the cancellation condition is satisfied is turned on (step S12), and this routine ends.

Conversely, if the driver does not intend to drive the vehicle and the result is negative in step S11, another control is used to determine whether or not there is a deceleration request (step S13). This step S13 is performed, for example, when deceleration support control such as pre-crash safety control (PCS control) is being executed to prevent a collision with an obstacle ahead or reduce damage caused by the collision. , the navigation system detects the gradient angle and the gradient direction of the road ahead, and if the gradient angle and the gradient direction of the road surface is a downhill road that requires engine braking force, etc., it is determined affirmatively. . That is, it is determined in step S13 whether a downshift is required for deceleration.

Therefore, if the determination in step S13 is affirmative because there is a deceleration request, the process proceeds to step S12, and the flag indicating that the cancellation condition is satisfied is set to ON. Conversely, if the determination in step S13 is negative because there is no deceleration request, the flag indicating that the cancellation condition is met is set to OFF (step S14), and this routine is terminated.

It should be noted that the cancellation conditions in steps S11 and S13 in FIG. 4 are only examples, and cancellation is based on various conditions such as whether or not cruising is not desirable, or whether shifting is desirable or not. You may judge the presence or absence of establishment of conditions.

As described above, by prohibiting gear shifting while driving in the busy shift range, even if the required driving force changes slightly due to factors such as changes in the road surface gradient and changes in the distance between the vehicle and the vehicle ahead. , it is possible to suppress occurrence of hunting caused by repeated shifts between the first forward speed stage and the second forward speed stage. Further, by maintaining the second forward speed, the change in the driving force with respect to the change in the output torque of the engine 1 can be made smaller than when the first forward speed is set, and the controllability of the driving force is improved. can be improved.

Note that the shift control device in the embodiment of the present invention is configured to prohibit shifting from the second forward speed on the high vehicle speed side that can be set. Alternatively, it may be configured to prohibit shifting from the first forward speed stage on the low vehicle speed stage side that can be set. In addition, the present invention is not limited to suppressing a busy shift between the first forward speed and the second forward speed. , when the vehicle is cruising at a speed between the coast down point at which the vehicle downshifts from the 4th forward speed to the 3rd forward speed during coasting, shifting from the 4th forward speed is prohibited. can be configured to

Furthermore, the gear shift control device according to the embodiment of the present invention can control an automatic transmission provided in a vehicle that runs by determining the required amount of engine power without the driver's accelerator operation. Therefore, it may be an automatic transmission provided in a so-called self-driving vehicle capable of automatically controlling the steering angle in addition to the driving force and the braking force. In that case, the vehicle may be a vehicle capable of only automatic driving, or a vehicle capable of switching between normal driving and automatic driving.

REFERENCE SIGNS LIST 1 engine 2 input shaft 3 automatic transmission 4 output shaft 8 drive wheel 9 cruise switch 10 inter-vehicle distance measuring instrument 11 electronic control unit (ECU)
12 Engine control unit 13 Shift control unit 17 Driving mode determination unit 18 Vehicle speed determination unit 19 Shift prohibition unit Ve Vehicle

Claims (10)

An input shaft connected to an engine, an output shaft connected to drive wheels, and a gear ratio between the input shaft and the output shaft are set to a predetermined gear ratio selected from a plurality of predetermined gear ratios. and a controller for setting the gear ratio of the transmission mechanism based on the power demand of the engine and the vehicle speed.
The controller is
A driving mode determination unit that determines whether the vehicle is automatically driving by determining the required amount of power of the engine without the driver operating the accelerator;
When power is required to be output from the engine, at a first vehicle speed or higher at which the first gear ratio is switched to a second gear ratio that is smaller than the first gear ratio, and power is output from the engine. a vehicle speed determination unit that determines that the vehicle is traveling at a vehicle speed lower than or equal to a second vehicle speed for switching from the second gear ratio to the first gear ratio when output is not requested;
When the driving mode determination unit determines that the vehicle is automatically traveling and the vehicle speed determination unit determines that the vehicle speed is equal to or higher than the first vehicle speed and equal to or lower than the second vehicle speed, the A shift control device for an automatic transmission, comprising: a shift prohibition section for prohibiting shifting from the 1st gear ratio or the 2nd gear ratio. In the shift control device for an automatic transmission according to claim 1,
The shift control device for an automatic transmission, wherein the shift prohibition unit prohibits shifting from the second gear ratio. 3. In the shift control device for an automatic transmission according to claim 1,
The controller is
The vehicle speed determination unit determines that the actual vehicle speed is equal to or greater than the first vehicle speed and equal to or less than the second vehicle speed during steady running in which a difference between a target vehicle speed for automatic travel and an actual vehicle speed is less than a predetermined difference. A shift control device for an automatic transmission, characterized in that: In the shift control device for an automatic transmission according to claim 3,
The shift control device for an automatic transmission, wherein the steady running includes running in which the difference between the target vehicle speed and the actual vehicle speed is less than a predetermined difference for a predetermined time or longer. In the shift control device for an automatic transmission according to claim 3 or 4,
A shift control device for an automatic transmission, wherein the target vehicle speed includes a vehicle speed preset for the automatic travel. In the shift control device for an automatic transmission according to claim 3 or 4,
It is further equipped with an inter-vehicle distance measuring device that measures the inter-vehicle distance with the vehicle ahead,
The automatic driving includes follow-up driving in which the vehicle-to-vehicle distance is maintained at a predetermined distance,
A shift control device for an automatic transmission, wherein the target vehicle speed includes a vehicle speed for maintaining the vehicle-to-vehicle distance at the predetermined distance. In the shift control device for an automatic transmission according to any one of claims 1 to 6,
The controller is
A shift control device for an automatic transmission, wherein a shift from the first gear ratio or the second gear ratio is permitted when a predetermined release condition is satisfied. In the shift control device for an automatic transmission according to claim 7,
A shift control device for an automatic transmission, wherein the predetermined release condition includes a condition that the driver performs a drive operation or a braking operation. In the shift control device for an automatic transmission according to claim 7,
A shift control device for an automatic transmission, wherein the predetermined cancellation condition includes a condition that there is a deceleration request by another control. In the shift control device for an automatic transmission according to claim 7,
Further comprising a sensor for detecting the slope angle and slope direction of the road ahead,
The automatic transmission, wherein the predetermined release condition includes a condition that the slope direction of the road surface in front is a descending direction and the slope angle of the road surface is equal to or greater than a predetermined angle. gear control device.

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